Carrier aggregation is enabled in Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) networks starting with Release 10. Carrier aggregation is where a User Equipment device (UE) receives on multiple carriers, which are referred to as component carriers, for the downlink or transmits on multiple component carriers for the uplink. Carrier aggregation is one of the ways of increasing the per-user throughput for UEs with good channel conditions with the capability of receiving and transmitting at higher data rates. A UE can be configured in two or three (or more) simultaneous bands in the downlink and/or the uplink.
FIG. 1A is a schematic diagram showing an example of a LTE Release 8 uplink from a UE to an enhanced or evolved Node B (eNB), or base station, and a downlink from the eNB to the UE on a single cell. This single cell has a single uplink carrier and a single downlink carrier. For Frequency Division Duplexing (FDD) mode, the uplink and downlink carriers are different carriers. For Time Division Duplexing (TDD) mode, the uplink and downlink carriers are the same carrier. In the example of FIG. 1A, the eNB is capable of running four different cells with respective uplink and downlink carriers at the same time. These cells are operated either in different bands or they could also be operated in the same band. In LTE Release 8, only one cell is used for communication between the eNB and the UE.
Conversely, carrier aggregation uses two or more component carriers in the downlink and/or two or more component carriers in the uplink. As such, there are many different scenarios for carrier aggregation. As a first example, Downlink (DL) Carrier Aggregation (CA) may use two downlink component carriers. This is referred to as 2 DL CA. For 2 DL CA, a single uplink carrier may be used. In this regard, FIG. 1B is a schematic diagram illustrating an example of 2 DL CA where there are two downlink component carriers and a single uplink carrier. Compared to FIG. 1A, in FIG. 1B, two of the cells are activated for the UE, which is the initial version of DL CA. In this case, the UE is configured to simultaneously receive downlink transmissions on two cells while transmitting on only one cell. The uplink allocation in this case is arbitrary, meaning that either of the cells can be used for uplink transmission. In carrier aggregation terms, the cell where the uplink is allocated for a certain UE is referred to as a Primary Cell (PCell) for that UE, while the other aggregated cell is referred to as a Secondary Cell (SCell). PCell and SCell combinations are UE specific.
FIG. 1C illustrates an example of 3 DL CA where the UE simultaneously receives on three downlink component carriers (i.e., on three cells) and transmits on, in this example, one uplink carrier (i.e., on one cell). While only one uplink cell is activated for the UE in this example, note that Uplink (UL) CA may also be used such that two or more cells may be activated for the UE for the uplink. The uplink may be allocated to any of the cells.
FIG. 1D illustrates an example of 2 UL CA where the UE simultaneously transmits on two cells for the uplink and, in this example, simultaneously receives on two cells for the downlink. Contrary to FIGS. 1B and 1C, FIG. 1D shows the case when UL CA is also enabled for the UE. In this case, only 2 UL and 2 DL CA is shown. In case of UL CA, PCell and SCell definitions are still UE specific.
Depending on the carrier frequency, or depending on the physical eNB deployment, the deployment of a carrier aggregation-enabled system can be very different. In this regard, FIGS. 2A and 2B provide two examples of a carrier aggregation deployment. FIG. 2A illustrates a deployment including a first set of cells on a first carrier frequency (F1) and a second set of cells on a second carrier frequency (F2). The F1 and F2 cells are co-located and overlaid, but the F2 cells have smaller coverage due to larger path loss. The F1 cells provide sufficient coverage, and the F2 cells are used to improve throughput. Mobility is performed based on the coverage of the F1 cells. One possible scenario to consider is when F1 and F2 are of different bands, e.g., F1={800 megahertz (MHz), 2 gigahertz (GHz)} and F2={3.5 GHz}, etc. It is expected that aggregation is possible between overlaid F1 and F2 cells.
FIG. 2B illustrates a different deployment in which the F1 cells provide macro coverage and the F2 cells are provided by Remote Radio Heads (RRHs) to improve throughput at hot spots. Mobility is performed based on the coverage of the F1 cells. A possible scenario is when F1 and F2 are of different bands, e.g., F1={800 MHz, 2 GHz} and F2={3.5 GHz}, etc. It is expected that the F2 RRH cells can be aggregated with the underlying F1 macro cells.
In LTE, the nominal number of Resource Blocks (RBs) is 6, 15, 25, 50, 75, and 100 RBs for channel bandwidths of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz, respectively, as shown in Table 1 below. The maximum limit on the uplink configurations in terms of allowed RBs, however, is pre-defined in the standard for different bands and carrier aggregation configurations to ensure that the UE meets one or more pre-defined receiver requirements, e.g. UE receiver sensitivity (aka REFSENS). The requirements on uplink configuration also depend upon channel bandwidth.
More specifically, the uplink configurations specified for different bands and different carrier aggregation configurations determine the uplink transmission block size in terms of RBs when a certain carrier aggregation configuration is used or when a single uplink is used. Three representative tables from 3GPP Technical Specification (TS) 36.101 (version 12.2.0) are presented below and show allowed uplink configurations when single uplink transmission, or inter-band carrier aggregation or intra-band non-contiguous carrier aggregation, respectively, is used. It is observed from Tables 1 through 4 that for certain bands, CA configuration and Bandwidth (BW) or BW combinations aka aggregated BW (e.g., Table 3 or 4) allowed in certain CA configurations (e.g. Table 3 or 4), the uplink configuration (i.e., maximum allowed uplink RBs) is reduced compared to the corresponding nominal values (i.e., in Table 1).
TABLE 1Transmission bandwidth configuration NRB in E-UTRA channelbandwidths for both UL and DLChannel bandwidth WChannel [MHz]1.435101520Transmission bandwidth615255075100configuration NRB
TABLE 2Uplink configuration for reference sensitivityE-UTRA Band/Channel bandwidth/NRB/Duplex modeE-UTRA Band1.4 MHz3 MHz5 MHz10 MHz15 MHz20 MHzDuplex Mode1255075100FDD26152550501 501FDD36152550501 501FDD4615255075100FDD561525251FDD625251FDD7255075 751FDD861525251FDD92550501 501FDD10255075100FDD1125251FDD12615201201FDD13201201FDD14151151FDD. . .17201201FDD1825251251FDD1925251251FDD2025201203 203FDD2125251251FDD222550501 501FDD23615255075100FDD242550FDD256152550501 501FDD2661525251251FDD2761525251FDD281525251251 251FDD3025251FDD316 54 54FDD. . .33255075100TDD34255075TDD35615255075100TDD36615255075100TDD37255075100TDD38255075100TDD39255075100TDD40255075100TDD41255075100TDD42255075100TDD43255075100TDD4415255075100TDDNOTE 1:1refers to the UL resource blocks shall be located as close as possible to the downlink operating band but confined within the transmission bandwidth configuration for the channel bandwidth (Table 5.6-1).NOTE 2:For the UE which supports both Band 11 and Band 21 the uplink configuration for reference sensitivity is FFS.NOTE 3:3refers to Band 20; in the case of 15 MHz channel bandwidth, the UL resource blocks shall be located at RBstart 11 and in the case of 20 MHz channel bandwidth, the UL resource blocks shall be located at RBstart 16NOTE 4:4refers to Band 31; in the case of 3 MHz channel bandwidth, the UL resource blocks shall be located at RBstart 9 and in the case of 5 MHz channel bandwidth, the UL resource blocks shall be located at RBstart 10.
TABLE 3Uplink configuration for reference sensitivityE-UTRA Band/Channel bandwidth/NRB/Duplex modeEUTRA CAEUTRA1.4 MHz3 MHz5 MHz10 MHz15 MHz20 MHzDuplexConfigurationband(dBm)(dBm)(dBm)(dBm)(dBm)(dBm)modeCA_2A-29A22550FDD29N/AN/AN/ACA_4A-29A42550FDD29N/AN/AN/ACA_23A-29A23255075100FDD29N/AN/AN/A
TABLE 4Intra-band non-contiguous CA uplink configuration for reference sensitivityCAAggregated channelUL PCCΔRIBNCDuplexconfigurationbandwidth (PCC + SCC)Wgap/[MHz]Allocation(dB)modeCA_3A-3A25RB + 25RB45.0 < Wgap ≤ 65.0 1214.7FDD0.0 < Wgap ≤ 45.0251025RB + 50RB40.0 < Wgap ≤ 60.0 1213.80.0 < Wgap ≤ 40.0251025RB + 75RB35.0 < Wgap ≤ 55.0 1213.60.0 < Wgap ≤ 35.02510 25RB + 100RB30.0 < Wgap ≤ 50.0 1213.40.0 < Wgap ≤ 30.0251050RB + 25RB30.0 < Wgap ≤ 60.0 1295.10.0 < Wgap ≤ 30.0321050RB + 50RB25.0 < Wgap ≤ 55.0 1294.30.0 < Wgap ≤ 25.0321050RB + 75RB20.0 < Wgap ≤ 50.0 1293.80.0 < Wgap ≤ 20.03210 50RB + 100RB15.0 < Wgap ≤ 45.0 1293.40.0 < Wgap ≤ 15.0321075RB + 25RB25.0 < Wgap ≤ 55.0  12106.00.0 < Wgap ≤ 25.0321075RB + 50RB20.0 < Wgap ≤ 50.0  12104.70.0 < Wgap ≤ 20.0321075RB + 75RB15.0 < Wgap ≤ 45.0  12104.20.0 < Wgap ≤ 15.03210 75RB + 100RB10.0 < Wgap ≤ 40.0  12103.80.0 < Wgap ≤ 10.03210100RB + 25RB 15.0 < Wgap ≤ 50.0  16116.50.0 < Wgap ≤ 15.03210100RB + 50RB 10.0 < Wgap ≤ 45.0  16115.10.0 < Wgap ≤ 10.03210100RB + 75RB 5.0 < Wgap ≤ 40.0 16114.50.0 < Wgap ≤ 5.0 3210100RB + 100RB0.0 < Wgap ≤ 35.0 16114.1CA_4A-4ANOTE 6NOTE 7NOTE 80.0FDDCA_7A_7A50RB + 50RB25.0 < Wgap ≤ 50.0 3210.0FDD0.0 < Wgap ≤ 25.05010.075RB + 25RB20.0 < Wgap ≤ 50.0 3210.00.0 < Wgap ≤ 20.05010.075RB + 50RB20.0 < Wgap ≤ 45.0 3210.00.0 < Wgap ≤ 20.05010.075RB + 75RB15.0 < Wgap ≤ 40.0 3210.00.0 < Wgap ≤ 15.05010.0100RB + 75RB 15.0 < Wgap ≤ 35.0 3610.00.0 < Wgap ≤ 15.05010.0100RB + 100RB15.0 < Wgap ≤ 30.0 3210.00.0 < Wgap ≤ 15.04510.0CA_23A-23ANOTE 6NOTE 7NOTE 80.0FDDCA_25A-25A25RB + 25RB30.0 < Wgap ≤ 55.0 1015.0FDD0.0 < Wgap ≤ 30.02510.025RB + 50RB25.0 < Wgap ≤ 50.0 1014.50.0 < Wgap ≤ 25.02510.050RB + 25RB15.0 < Wgap ≤ 50.0 1045.50.0 < Wgap ≤ 15.03210.050RB + 50RB10.0 < Wgap ≤ 45.0 1045.00.0 < Wgap ≤ 10.03210.0CA_41A-41ANOTE 6NOTE 7NOTE 80.0TDDNOTE 1:1refers to the UL resource blocks shall be located as close as possible to the downlink operating band but confined within the transmission.NOTE 2:Wgap is the sub-block gap between the two sub-blocks.NOTE 3:The carrier center frequency of PCC in the UL operating band is configured closer to the DL operating band.NOTE 4:4refers to the UL resource blocks shall be located at RBstart = 33.NOTE 5:For the TDD intra-band non-contiguous CA configurations, the minimum requirements apply only in synchronized operation between all component carriers.NOTE 6:All combinations of channel bandwidths defined in Table 5.6A. 1-3.NOTE 7:All applicable sub-block gap sizes.NOTE 8:The PCC allocation is same as Transmission bandwidth configuration NRB as defined in Table 5.6-1.NOTE 9:9refers to the UL resource blocks shall be located at RBstart = 25.NOTE 10:10refers to the UL resource blocks shall be located at RBstart = 35.NOTE 11:11 refers to the UL resource blocks shall be located at RBstart = 50.
Maximum Power Reduction (MPR) is defined as allowed reduction to maximum output power due to higher order modulation and transmit bandwidth configuration. The general MPR formula is defined in the UE specification 3GPP TS 36.101 since Release 8 for different transmission modes, e.g. single uplink transmission, 2 UL CA transmission, etc. The UE applies the MPR based on uplink transmission parameters, e.g. modulation, uplink configuration, carrier aggregation type or configuration, etc. Additional MPR (A-MPR) is defined for certain bands which are allowed to be applied on top of MPR for certain bands. A-MPR is usually defined for specific coexistence requirements, etc. The A-MPR is signaled to the UE by the network node. Both MPR and A-MPR are used by UEs to comply with one or more radio emission requirements, e.g. out of band emission, spurious emission, or additional spurious emission requirements.
Currently, there are several types of carrier aggregation, and the different types of carrier aggregation may have different configurations in terms of number of component carriers and available uplink physical resources (e.g., uplink RBs). In certain carrier aggregation configurations (e.g., non-contiguous carrier aggregation with one uplink component carrier and especially in two or more uplink component carriers), the available uplink physical resources on one or more uplink component carriers are very low compared to the maximum number of uplink RBs. The maximum number of uplink RBs is equal to channel bandwidth. For example, as shown in Table 4, in some cases the uplink RBs can be as small as 12 RBs even though the bandwidth of the corresponding uplink component carrier can be as large as 50 RBs. This in turn may significantly degrade the UE performance in uplink, e.g., decrease uplink user throughput. However in some cases the reduction in uplink throughput may be acceptable for the UE.
As such, there is a need for systems and methods for improving performance when using carrier aggregation.